Brain Stem and cortical control of motor function. Dr Z Akbari

Size: px

Start display at page:

Download "Brain Stem and cortical control of motor function. Dr Z Akbari"

Jemima Porter
5 years ago
Views:

1 Brain Stem and cortical control of motor function Dr Z Akbari

2 Brain stem control of movement BS nuclear groups give rise to descending motor tracts that influence motor neurons and their associated interneurons (posture, locomotion, and eye movements) Red nucleus (magnocellular part) Vestibular nuclear complex Reticular formation Tectum Dr Z Akbari

3 Medial and lateral descending pathways from the brain stem A. Medial pathways: Main pathways for maintaining posture & head position during movem Descend in the ventral column. Terminate in the ventromedial spinal gray matter. Pontine(+) and medullary(-) reticulospinal pathway. Lat. VS tract Med.VS tract Tectospinal tracts B. Lateral pathway : Important for the production of movement, especially in the distal limbs Rubrospinal tract (magnocellular portion of the red n). Descends in the contralateral dorsolateral column. Terminates in the dorsolateral area of the spinal gray matter.

4 Dr Z Akbari

5 Dr Z Akbari

6 Cortical motor function Dr Z Akbari

7 The motor cortex and corticospinal tract Primary Motor cortex (4) Premotor control area (6) Supplementary motor area

8 Control of voluntary movement Dr. Z akbari

9 Primary motor cortex Control simple feature of movement Activity of cortical neurons signals direction and amplitude of muscle force required to produce movement rather than actual displacement of joint* Premotor control area Controls complex movement involve multiple joint (reaching & grasping) Receive fiber from area 5 & 7.send to M1 Mental rehearsal of movement Movement triggered by external event involved PMv Supplementary motor area Coordinates bilateral movements. Movement triggered internally involved SMA Prepare movement sequences in the absence of visual Dr. cues Z akbari

10 Population activity in the motor cortex Black lines are individual cell vectors. When all of them are summed for a particular direction of movement, the resulting population vector (red) Dr. Z akbari points in essentially the direction of the upcoming movement.

11 Some specialized area of motor cortex Boca's area Voluntary eye movement field Head rotation area Area for hand skill Dr. Z akbari

12 Somatotopic organization of primary motor cortex Plasticity: change of motor maps with experience Dr. Z akbari

13 Corticospinal tract (Pyramidal system) Corticospinal tract: lat & ventral Primary MA: 30% Premotor &SMA: 30% Somatosensory area: 40% Giant pyramidal cells (Betz cell) Extrapyramidal system: Descending BS & spinal pathways that do not pass through pyramid. -Postural control

14 The cortex directly controls motor neurons in the SC and BS through descending pathways: A. The vent. corticospinal tract : o Premotor area (6) and a zones in area 4 controlling the neck and trunk. o The descending fibers terminate bilaterally o Send collaterals to the medial pathways from the BS. B. The lat. corticospinal tract: otwo motor areas (4 & 6) and three sensory areas (3, 2, & 1). oit crosses at the pyramidal decussation, othe fibers from the sensory cortex terminate primarily in the medial portion of the dorsal horn. Collateral fibers project to dorsal column nuclei. (allow the brain to actively modify sensory signals). C. The corticobulbar tract : Lat: ends contralaterally in the part of the facial nucleus that supplies muscles of the lower face and in the hypoglossal nucleus. Med :The remainder of the corticobulbar tract ends bilaterally. Dr. Z akbari

15 Dr. Z akbari

16 Other pathways from the motor cortex Betz cell collateral Fibers to basal ganglia Fibers to red nucleus Fibers to BS: vestibular nuclei and reticular substance Fibers to pontine nuclei: corticopontocerebellar fiber Fibers to olivary nucleus cerebellum Corticobulbar pathway Incoming pathways to the motor cortex From other cortical area (Parietal, frontal, occipital, temporal) From opposite cerebral hemisphere Somatosensory fiber Tract from VL & VA n of thalamus ( from basal ganglia & cerebellum) Fiber from intralaminar nuclei of thalamus: general excitability Dr. Z akbari

17 Dr. Z akbari

18 Descending motor pathways Lateral system: Lat CS tract Rubrospinal tract Concerned with goal directed movemnet Medial system: Ventral CS Reticulospinal Med & Lat Vestibulospinal Tectospinal Provide basic postural control system Dr. Z akbari

19 Dr Z Akbari

I: To describe the pyramidal and extrapyramidal tracts. II: To discuss the functions of the descending tracts.

Descending Tracts I: To describe the pyramidal and extrapyramidal tracts. II: To discuss the functions of the descending tracts. III: To define the upper and the lower motor neurons. 1. The corticonuclear